In recent years, light-emitting devices using group III-V nitride semiconductor typified by gallium nitride (GaN) have been expected as next-generation illumination light sources because they can provide light emission in the short wavelength region. Therefore, active research and development is being conducted on the devices (see, for example, Patent Document 1).
Such light-emitting devices are required to have a decreased operating voltage and an enhanced optical power output. To meet this requirement, the devices have employed, instead of insulating substrates such as sapphire substrates, conductive substrates made of group III-V nitride semiconductor such as GaN. In the case of employing the conductive substrate, current is passed in the substrate. Therefore, the resistances of current paths in the device can be reduced to decrease power consumption and the operating voltage of the device, and concurrently to enhance the static breakdown voltage of the device.
FIG. 16 shows a cross-sectional structure of a conventional light-emitting device. Referring to FIG. 16, an n-type semiconductor layer 102 of GaN, a light-emitting layer 105 of indium gallium nitride (InGaN), and a p-type semiconductor layer 106 of aluminum gallium nitride (AlGaN) are sequentially stacked on a substrate 101 made of n-type GaN. A p-side electrode 107 is formed on the p-type semiconductor layer 106. Respective portions of the p-type semiconductor layer 106, the light-emitting layer 105, and the n-type semiconductor layer 102 are etched to expose a portion of the n-type semiconductor layer 102, and then an n-side electrode 108 is formed on the exposed portion of the n-type semiconductor layer 102 (see, for example, Patent Document 2).
(Patent Document 1) Japanese Unexamined Patent Publication No. 2001-60719
(Patent Document 2) Japanese Unexamined Patent Publication No. 2001-345476